October 21-31 1999 - The ITD/ITF over West Africa retreated 1.6 degrees of latitude during October 21-31 to 13.6 degrees north lat. This was still 0.9 degrees north of its 20-year mean position and the fifth consecutive period it was north of normal. The ITD was either at or north of its normal location every period since the start of July. Consistent with this pattern are the reports of abundant rains across the Sahel countries this growing season, with many reports of flooding. The June-September ITD average was this far north only in 1981, 1988, and 1994. The slow start of the season in June prevented this year's ITD from setting a seasonal record. In East Africa, the ITD for October 21-31 retreated 1.3 degrees to 12.9N, or 1.4 degrees north of normal. This was the 11th consecutive period the ITD was north of normal. The Jun-Sep mean position of 16.3N was easily the farthest north since recording began in 1989.

This is the last update planned for this year. The ITD updates for Y2K should start next April.

October 11-20 1999 - The ITD/ITF retreated southward by 1.7 degrees latitude across West Africa to 15.2 N. This was 0.9 degrees north of its long-term mean position and the 11th consecutive week the ITD was at or north of normal. Over eastern Africa, the ITD retreated 1.8 degrees to 14.2 N, which was 1.3 degrees north of the long-term mean and the 10th consecutive week it was north of normal.

October 1-10 1999 - The ITD/ITF over West Africa only retreated 0.1 degrees latitude to 16.9 N. This contrasts with the 20-year average for this date of 15.5 N, and breaks a record for the farthest north recorded since at least 1979, when these records began. This was the 10th consecutive week the ITD was at or north of normal, and is consistent with the above-normal rains recorded over the Sahel since July. To the east, the ITD over 20 to 35 degrees east longitude averaged 16.0 N, or 2.1 degrees north of the long-term mean and only 0.5 degrees south of the previous period. This broke a record for the farthest north recorded during the period of record, which begins in 1988. This was the 9th consecutive week the ITD was north of normal over the eastern Sahel. Rainfall during October 1-10, 1999 was well above-normal in central Sudan, which is consistent with the ITD position.

September 21-30 1999 - During Sep 21-30, 1999, the ITD/ITF retreated to 17.0 degrees north over West Africa, 1.4 degrees south of its previous position. This was 0.5 degrees north of normal, and the 9th consecutive week the ITD was at or north of its normal location. For the Jun-Sep season, the ITD averaged 18.2 N, which was 0.4 degrees north of its long-term mean position and 0.2 degrees north of last year's position. In the east, the ITD averaged 16.5 degrees north, which was 1.5 degrees north of normal and 0.1 degree north of the previous period's position. This was the 8th consecutive week the ITD was at or north of normal in eastern Africa. For the Jun-Sep season, the ITD averaged 16.2 degrees north, which was 0.6 degrees north of normal and 0.3 degrees north of last year's position. The persistent northward tendency of the ITD is consistent with the abnormally heavy rains that have affected the Sahel region since July.

September 11-20 1999 - During September 11-20, 1999, the ITD/ITF was located near 18.4 degrees north, which was 0.9 degrees north of the long-term mean position and 0.2 degrees north of the September 1-10, 1999 position. It is quite unusual for the ITD to move northward in September instead of retreating southward, and this implies that the Sahel rainy season remains active. To the east, however, the ITD continued its retreat, with the mean ITD during September 11-20 retreating 0.7 degrees to 16.4 N, which is 0.7 degrees north of its long-term mean position.

September 1-10 1999 - The ITD/ITF began retreating southward in September, which is expected. In West Africa (10 degrees W to 10 degrees E), the ITD averaged 18.2 degrees N during Sep 1-10, 1999 vs 20.8 N the prior week and 18.2 N for the long-term mean. This change to normal comes after 6 consecutive weeks north of normal, resulting in above-normal rains for the Sahel countries from July until now.

In East Africa (20-35 degrees E), the ITD averaged 17.1 N during Sep 1-10 vs 17.6 N the prior week and 16.0 N for the long-term mean. This was the 6th consecutive week the ITD was north of normal in the east.

August 21-31 1999 - During August 21-31, 1999, the ITD/ITF over West Africa remained north of normal for the sixth consecutive period. Its mean location was 20.8 degrees north latitude, which was 0.3 degrees north of the prior period and 1.8 degrees north of the 20-year mean. This was the farthest north location of the year and the farthest north of any 10-day period since August 21-31, 1988, which was the record since 1979. In East Africa, the ITD/ITF dropped 1.0 degrees from the prior period to 17.6 N. This was 0.8 degrees north of the recent normal and the fifth consecutive week it was located north of normal.

August 11-20 1999 - The ITD remained at the previous period's position of 20.5 degrees north latitude over West Africa. This is 1.2 degrees north of normal, and sets a 20-year record for the second consecutive period. In the east, the ITD advanced 0.3 degrees north to 18.6 N, or 1.4 degrees north of average. In the west, this was the 5th consecutive week the ITD was north of normal. In the east, this was the 4th week north of normal.

August 1-10 1999 - The ITD over West Africa advanced 0.5 degrees north to 20.5 degrees north latitude. This was 1.4 degrees north of the 20-year mean and the fourth consecutive week the ITD was north of normal. This was also the farthest north the ITD has been for August 1-10 since records began in 1979. Over eastern Africa (20 to 35 degrees east), the ITD advanced to 18.2 degrees N, which was 0.2 degrees north of the previous location and 1.3 degrees north of the average for August 1-10. This was the third consecutive week the ITD was north of normal. Consistent with the northward displacement of the ITD/ITF, rains have been generally heavy across the Sahel, with flooding reported in Mali and Chad. To the south, rainfall has recently been below normal along the Gulf of Guinea coast.

July 21-31 1999 - The ITD made good progress northward, with the ITD in West Africa advancing to 20.0 degrees latitude north, 1.1 degrees north of the 20-year mean and 1.0 degrees north of last period's location. This was the third consecutive week the ITD was north of normal. In the east, the ITD advanced to 18.1 N, or 1.9 degrees north of the average location and 1.1 degrees north of last period's position.

July 11-20 1999 - The ITD/ITCZ made significant progress advancing northward across Africa, actually moving north of its long-term mean location. The ITD over West Africa was positioned at 19.2 degrees north latitude during July 11-20, which was 0.9 degrees north of its 20-year mean position and 1.6 degrees north of its position during July 1-10, 1999. As a result, rainfall was quite widespread across the Sahel and there were signs of the mini dry season beginning along the immediate Gulf of Guinea coast of West Africa. In East Africa, the ITD advanced northward to 17.0 degrees N, which was 1.1 degrees north of its average location for July 11-20 and 1.9 degrees north of its prior location.

July 1-10 1999 - The ITD/ITCZ made significant progress advancing northward across Africa. After 4 weeks of being south of normal, the ITD was finally positioned near its typical location for July 1-10 in West Africa. Its location averaged 17.6 degrees north latitude during July 1-10, which was 0.1 degrees north of its 20-year mean position and 1.3 degrees north of its position during June 20-30. As a result, rainfall improved across much of the Sahel. In East Africa, the ITD advanced to 15.1 degrees N, which was at the average location for July 1-10 and 1.1 degrees north of its prior location.

June 21-30 1999 - The ITD/ITCZ advanced 0.9 degrees latitude north over West Africa to 16.3 N. However, this was the 4th consecutive period the ITD was south of its 20-year mean position. The long-term mean position for June 21-30 is 17.0 N. For the month of June, 1999, the ITD averaged 15.5 N. This was the farthest south of record. Over East
Africa, the ITD advanced 1.0 degrees N, putting it near the average of 14.4 N.

Consistent with the ITD movement, the seasonal rains have been slow to start in the Sahel. However, rainfall increased both in the western Sahel and to the south over the Gulf of Guinea countries during July 1-10, 1999.

June 11-20 1999 - The ITD/ITF over West Africa advanced northward to 15.4 degrees north from 14.8 N the previous period. This contrasts with the 20-year mean position of 16.4 N, and was the farthest south for this date since readings began in 1979. This makes the second consecutive 10-day period the ITD was located at a record south position, and implies the rains are much slower driving north than usual. The rainfall and temperature data confirm that the rains have been late in the Sahel, especially from Mali to Chad.

In East Africa, the ITD was also significantly south of normal, averaging 13.3 N during June 11-20, which is 0.9 degrees south of the 9-year mean and 0.6 degrees south of last year's position. This was a retreat southward of 0.1 degrees since June 1-10 and the farthest south position for this date since 1990. As in West Africa, rainfall and temperature data confirm that abnormally dry weather prevailed across central Sudan during this period.

June 1-10 1999 - The ITD/ITF over West Africa retreated to the farthest-south latitude measured since readings began in 1979. The mean position between 10 degrees W longitude and 10 degrees E longitude was 14.8 degrees N. In contrast, the 20-year mean position is 16.0 N and last year's position was 16.8 N. The ITD was especially depressed near E. Mali, Burkina Faso, and Niger, where it was 2 to 3 degrees south of last year's position. This is consistent with the rainfall data, which indicate abnormally dry weather from Mali to Niger.

In East Africa, the ITD was also south of normal, averaging 13.4 N during June 1-10, which is 0.3 degrees south of the 9-year mean and 0.6 degrees north of last year's position. This was a retreat from the May 21-31, 1999 position of 14.2 N.

May 21-31 1999 - the ITD/ITF advanced northward 0.5 degrees latitude to a mean position of 15.1 degrees N over West Africa (10 degrees W to 10 degrees E). This was 0.3 degrees south of its 20-year mean position for May 21-31 and 1.2 degrees south of its position one year ago. The ITD typically advances 0.8 degrees north from May 11-20 to May 21-31, so its progress has been slower than normal and, by implication, the seasonal rains slowed their advance northward into the Sahel. The mean monthly position for May 1999 was 14.4 degrees N, which was 0.3 degrees south of the long-term mean. In East Africa, in contrast, the ITD during May 21-31 1999 was located near 14.2 degrees north, or 1.4 degrees north of its
long-term mean.

May 11-20 1999 - the ITD's location over West Africa (10 degrees W to 10 degrees E) averaged 14.6 degrees N latitude, which was at the 20-year mean (1979-98). This was 1.0 degrees north of the May 1-10, 1999 mean (13.6). The April 21-30, 1999 average position was 13.9 N. In eastern Africa (20 to 35 degrees E), the ITD averaged 12.6 N during May 11-20, 0.3 degrees north of the long-term mean and 0.1 degree south of the May 1-10 position.

The progress of the seasonal rains, as deduced from the ITD data, was ahead of normal across West Africa in late April, but has recently been closer to normal. In eastern Africa, the rains' progress northward appeared to have slowed or stopped between early and mid-May.